The couple met through a stylist in 2007 while he was filming Indiana Jones, he tells Playboy.
"[I was] filming a sword fight when I got the message. I said, 'Can this be my life?'" he says.
The duo set up a dinner date over text message -- but they never developed much of a relationship.
"It never got beyond one date," he says. "The spark wasn't there. We weren't passionate about each other in that way, so we remain friends."
Maybe Rihanna didn't measure up to another woman in his life: mom.
"Probably the sexiest woman I know is my mother," LaBeouf says in the same interview. "She's an ethereal angel. Nobody looks like that woman. If I could meet my mother and marry her, I would. I would be with my mother now, if she weren't my mother, as sick as that sounds."